Move embedding and linking Flutter frameworks into the tool (#51453)

* Move embedding and linking Flutter frameworks into the tool

* Unused import

* Migrate

* Rename run, add comments, remove typedef

* Add status log to tell the user what we did

* Remove Podfile migration, create IOSMigration superclass

* word-smiting

Co-Authored-By: Jonah Williams <jonahwilliams@google.com>

* for space

Co-Authored-By: Jonah Williams <jonahwilliams@google.com>

Co-authored-by: Jonah Williams <jonahwilliams@google.com>